In a typical installation of a telecommunications system, data communications system, computer equipment, servers, and the like, power is almost always supplied by a massive rechargeable storage battery system with sufficient capacity to carry the system through any power outages or interruptions. The battery system is completely clamped at the sum of individual cell voltages and any primary power interruptions are completely bridged. Hence, any powerline-frequency ripple coming from the external source is completely absorbed. The battery system can supply the equipment with the DC voltage and can completely isolate any equipment attached thereto from utility outages, ripple, and other problems with the external power source. Battery drain is kept small by a charging current that is continuously furnished from an external high voltage AC source, such as a utility main line or an uninterruptable power supply (UPS). The system chooses between the utility source or the UPS with a static transfer switch. The high voltage AC output from the static transfer switch is then input to a transformer/rectifier device that supplies the needed charging current. However, conventional static transfer switches and transformer/rectifier devices typically provide no redundancy capabilities. Hence, failure of one of the components of these devices requires shutting the device down to replace the damaged component. Because the battery system is no longer being charged, it can sustain the system only for a limited number of hours, after which failure of the battery supplied power will result.
Conventional battery systems typically distribute the DC power at voltages close to the final application voltages. Since losses are proportional to current squared times the resistance (I2R), keeping I2R losses down has required conventional battery systems to employ expensive, bulky, and not readily reconfigurable, bus-bar current distribution systems to carry the high current, low voltage DC power close to the point of use.
In the past, the conventional battery based systems have been adequate. However, the recent explosion in demand for data communications and computer services makes the shortcomings of battery based systems clear. Prior battery based systems are expensive, massive, inflexible and occupy too much space. Moreover, the environmental hazards associated with the toxic waste created during battery manufacturing and disposal are increasingly intolerable.
To date, high voltage DC power distribution has been impractical because of the lack of an economical and scalable DC-DC voltage down-converter. Very large Ultra HVDC converters have been in use for many years, but they require gigantic installations and are completely unsuited to scaling down for the purpose of distributing DC power at common distribution voltages needed for a telecommunications system or a data communication system.